And I'm Steve Inskeep in Las Vegas. When President Trump visits here today, he arrives in a city where investigators are hard at work.

RACHEL MARTIN, HOST:

They're talking to the shooter's girlfriend, who has just returned to the U.S. from the Philippines. They're also reconstructing Sunday night's mass shooting. And investigators have learned the story begins well before Sunday. Steve, you are there. What have investigators learned about the shooter's preparations?

INSKEEP: Well, they're giving an image of a man who made meticulous preparations for quite some time. We'd already heard, of course, of his 23 weapons in the hotel suite at the Mandalay Bay Resort. We've also been told now by the Clark County Sheriff's office that he had cameras that he had mounted in the room, in the suite, so that he could watch police approaching. He expected, at some point, that people would be coming after him.

How was he able to do that? Well, he was a customer. It was his room. He had days to do what he wanted to do. And when you think about that, you realize what authorities are up against if you have an attacker who's going to be this sophisticated about his approach. And the investigation into that approach continues, of course, amid the debate over whether the law should ever have allowed anybody to assemble the kind of arsenal that Stephen Paddock did.

MARTIN: Yeah. And the president has added to the debate - the inevitable debate about gun control. He said gun laws would be talked about, quote, "as time goes by." What's that really mean, though?

INSKEEP: Well, exactly. I mean, that's going to be the question going forward is going to be not - are you going to talk sympathetically about gun control? - but is there something practical that you believe you can do that is politically possible?

MARTIN: NPR national political correspondent Mara Liasson has been thinking about all this stuff, covering it from here in Washington.

Mara, the debate is up again about gun control. What are Republican lawmakers saying in this moment?

MARA LIASSON, BYLINE: Well, what Republicans and the White House are saying is that now is not the time to discuss gun restrictions, especially so soon after this massacre, although President Trump has several times in the past after mass shootings by Muslims called for policy solutions right away, particularly his Muslim ban. But Democrats do want to try to do something to prevent or mitigate this kind of mass carnage. And they are talking about banning or trying to ban accessories like the bump stock that the Las Vegas shooter used to convert his semi-automatic weapon into something more like a machine gun.

MARTIN: The president will be in Las Vegas today. Any indications about if he's going to broach gun control in any way?

LIASSON: Well, I think he'll be asked, if reporters get a chance to ask him today. One effect that the Las Vegas shooting does appear to have had on gun legislation is to slow down efforts by Republicans that would loosen restrictions on the sale of gun silencers. This was a bill working its way through the House, supported by the president's son, Don Jr. Yesterday, the House speaker, Paul Ryan, said that there would not be a vote on that anytime soon.

MARTIN: The president was in Puerto Rico yesterday, consoling people there, tending to a very different kind of tragedy. He got some pushback for how he used that moment to talk about how expensive recovering Puerto Rico is going to be. Let's listen to that tape.

(SOUNDBITE OF ARCHIVED RECORDING)

PRESIDENT DONALD TRUMP: Now, I hate to tell you, Puerto Rico, but you've thrown our budget a little out of whack.

MARTIN: What are we learning, Mara, about how the president navigates these kinds of tragedies, these emotional kinds of situations?

LIASSON: Well, I think there are two very different situations. And you've seen two very different responses from the president, mostly on Las Vegas. So far, he has really stuck to the script. He's offered condolences and words of unity, much like presidents in the past have done after incidents like this. That's kind of teleprompter Trump. But in Puerto Rico and in the run-up to his visit, you really saw Twitter Trump. He made a series of combative and disparaging remarks about Puerto Rico and Puerto Ricans. Then he went to visit. As you said, he seemed most concerned with the reviews that the U.S. efforts were getting. And he seemed happy about those reviews.

He also made some news. He told Fox News that Puerto Rico's debt to Wall Street would have to be, quote, "wiped out." We're not exactly sure what he's talking about there. Recently, Puerto Rico declared a form of bankruptcy. They do owe $74 billion to Wall Street. And, of course, they've suffered about $90 billion worth of damage in the hurricane. So it's unclear what the president wants to do about that, but he seems to be open to some kind of debt relief.